Stabilizing sheet vulcanized fiber



Patented Jan. 28, 1936 UITED STATES PATENT OFFICE Herbert R. Stratford, Cleveland, Ohio, assignor to Horace B. Fay, Cleveland, ()hio No Drawing. Application August 28, 1931, Serial No. 559,925

6 claims. (or. 9168) The so-called vulcanized fiber" or cellulose treated chemically to toughen its fibrous structure has many excellent properties, but along with these there is an objectionable tendency to distortion and warping. So sensitive is the material that such changes occur merely in exposure to the atmosphere. These variations are more serious in thinner sheets. Notwithstanding its other qualifications, such material has accordingly been considered inapplicable for certain uses. In accordance with the present invention however, it now becomes possible to inhibit this dimculty and utilize the material in accordance with its other desired properties.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but a few of the various ways in which the principle of the invention may be employed.

' Vulcanized fiber sheet stock is usually made by treating sheeted cellulose or paper in a strong solution of zinc chloride, and washing out the residual treating agent, and drying. Equivalent halogen salts, sulphuric acid, etc., are sometimes used, or other treatment, the action being a par tial gelatim'zing and hydration of the fibers of cellulose. Hydrated cellulose greedily attracts water and it cannot be stabilized while subject to the action of this variable. It likewise also attracts oxy-carbon compounds, as alcohol, acetone, etc., particularly where these are present unguarded by other agents. The fiber stock in whatever way initially made, is in accordance with the present invention dried in a suitable drier to a minimum or constant moisture-content, i. e., practical dryness. For example, the vulcanized fiber may be dried at a safe moisture expelling temperature which may be up to 200 F. The sheet material is then sealed by an atmosphere-excluding sealing agent, this being applied in liquid form, as for instance by immersion or other suificient covering application, and after removal of the superfluous liquid,- if such be present, setting or drying the surface to a non-teem condition. Resin-like agents made from urea, in greater or less complexity, have been found by me to especially work well with vulcanized fiber.

The invention will be readily understood by reference to illustrative examples, as follows:-

I. Vulcanized fiber sheet is oven-dried at a moisture-expelling temperature, for instance up to 215 F., to substantially constant weight. as shown by sampling, and is then submerged in a bath made up of an alcoholic solution of 25 per cent of urea-rosin, about 25 per cent of japan wax, and about 50 per cent of a soluble phenolformaldehyde condensation product (the percentages referring to the relative proportions of the solid substances). The amount of alcoholic solvent may vary, for instance equal parts or more up to 2 times the amount of total solids. The urea-rosin referred to is preliminarily prepared by heating a mixture of 88 per cent rosin and 12 per cent urea to molten temperature, until the urea is incorporated, this taking place in a few minutes after molten temperature is reached. 15 The sheet fiber does not require long treatment in the liquid, a few moments affording a sealing action, although more prolonged treatment may be worth while with some stocks. The sheet material is dried by evaporation of the volatile solvent, and is ready for use. In the case, for instance, of such articles as discs, or shaped objects, it is desirable that the cutting or shaping be performed before the present treatment, although this is not essential in all cases.

II. Sheet vulcanized fiber of 10 mil. thickness is heated in a drier to substantially constant weight, as shown by sampling, and is treated with a liquid benzol-thinned mixture of boiled linseed oil 75 per cent, non-drying oil 10 per cent, and about 15 per cent of rosin-urea (made by heating rosin 88 per cent and urea 12 per cent to molten point and combination). The amount of benzol thinner for the foregoing may vary, for instance 10-150 per cent. The sheet material is dried by evaporation of the volatile solvent and by further setting of the drying oil, and is ready for use.

HI. Vulcanized fiber sheet is dried to substantially constant weight, and is immersed in a molten bath of about 60 per cent asphalt, 25 per cent rosin, and about 15 per cent japan wax. Surplus liquid is removed by doctor-blades or squeeze rolls, and the product is set by cools.

Other materials may be used more or less advantageously. In general though, it will be noticed that nitro-cellulose base solutions, hardsetting drying oil compositions and the like, are less desirable on account of their tendency to destroy the degree of flexibility otherwise to be had in the sheet.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or-the equivalent/oi such, be employed.

I therefore particularly point out and" distinctly claim asiny invention:'-

1. A method of inhibiting distortive change in sheet vulcanized fiber, which comprises expelling moisture from the fiber; and sealing the surface sheet vulcanized fiber, which" comprises expelling moisture from the fiber, and'sealingthe sur-- face with a settable iiquid'composition including urea-rosin, a wax and a phenol formaldehyde condensation product.

"sation product.

3. A vulcanized fiber sheet stabilized against distortion bg-r-an atmosphere-seal including japan wax-"and a phenol formaldehyde condensation product and urea rosin.

4:A"vulca nized' fiber sheet stabilized against distortion by an --atmosphere-seal essentially of a pu'ea'rosincondensation product mixed with other syntheticresin 5.""Avulcanized fiber sheet stabilized against distortion by an atmosphere-seal including arearosin and a wax.

EA vulcanized fiber sheet stabilized against distortion by an atmosphere-seal including arearosin,- a wax and a phenol formaldehyde conden- 'HERBERTR. STRA'I'FORD. 

